Cleft grafts are invasive and have the least odds of working with stone fruit, especially cherries. European ‘plums’ (or in my neck of the woods, “prunes”) are easier than Asian plums. Dormant grafts are best done early on ‘stone fruit,’ that’s fruit with ‘pit seeds.’ I’ve never made a bark graft on a cherry tree, but the way their bark ‘circles’ the tree would cause me to make very distinctive cuts to keep that from happening. But I’ve never found any warning against it… I’ve also had some major failures cleft grafting cherries.

If your scions are dormant, a bark graft would be a good alternative. …slipping bark is a good question; I’ve learned to be far more patient than I’d care to be… I’m thinking April will be safe. I’m looking to do some myself but want to see some good leaf formation first. Sacrificing an end stem may be the best indicator; cut it, break it, and if the bark ‘slips’ away from the wood – it should be good. If it ‘tears,’ not yet!